Here and hereinafter the term “cuff” is intended to mean an inflatable balloon attached around a tube, e.g. a tracheal tube. In tracheal tubes the purpose of the cuff is to function as a seal between the tube and the trachea, in order to prevent air from getting out and bacteria to enter the lungs. In other catheters, e.g. urine catheters, the purpose of the cuff is to block and secure the tube in the body part where it is inserted into.
Tracheal tubes are used as means of conveying air or gas mixtures delivered by an Intensive Care Unit or Anaesthesia ventilator, through a breathing circuit, into the patient airways. Tracheostomy cannulas can have the same use as tracheal tubes or are just installed on spontaneously breathing patients who for a particular disease or accidental reasons cannot breath autonomously and sufficiently without this airway bypass.
Usually, the cuff is obtained through a blowing process or an alternative technology of pre-extruded tubing expansion. The assembly process of the cuff on the tube consists of the following phases: cutting of the cuff ends, named collars; insertion of the so obtained cuff on the tube and correcting its positioning; and gluing with solvents or adhesive.
The result obtained from the above process is the formation of a kind of step next to the collar cutting edge. This step represents a traumatic factor during intubation operation because of the possible abrasions it can cause. This problem is particularly serious for children and infant patients where the diameter of the tubes is narrower and the collar thickness is crucial.
Another problem of the prior art process relates to manufacturing issues. In fact, the shaping and the assembly operations render the whole process slow, expensive and relying heavily on personnel experience and ability. It is important to notice that such problems become more relevant when the tube has a narrow diameter (e.g. for children and infant patients) and when the cuffs are made of polyurethane with reduced thickness and easy to be damaged during handling, tubing and gluing.
A way to overcome the above drawbacks is disclosed in for example, EP1733752A1, the entire contents of which is hereby incorporated by reference. This patent discloses a method to obtain a tube provided with an external sheath with which the cuff is formed. This method provides the adding of an anti-adherent agent in the zone of the cuff shaping. As it can be obvious for a person skilled in the art, the presence and the use of an anti-adherent agent can however involve a series of technical and economic inconveniences.
Accordingly, there is a need for manufacturing a cuff on plastic tubes provided with an external sheath whose technical characteristics are such to avoid the use of anti-adherent materials.